1. Field of the Invention
The present invention generally relates to the art of automotive vehicles, and more specifically to a wheel for a vehicle incorporating a sensor for continuously monitoring the air pressure in a tire mounted on the wheel during operation of the vehicle.
2. Description of the Related Art
Low tire pressure is a primary cause of excessive fuel consumption, tire wear and impaired steerability. A normal tire will typically leak on the order of 25 percent of its pressure per year due to its inherent permeability. It is thus good practice to maintain tire pressure on a regular basis.
However, even checking tire pressure every few weeks may not prevent these adverse affects when a slow leak is present, and the leak may go undetected unless a careful record is maintained of how frequently the pressure in each tire has to be replenished. A fast leak or flat condition can rapidly cause damage to the tire and even render it unusable in a short period of time, but this condition may go unnoticed by an inexperienced driver until it is too late.
It is thus highly desirable to have some mechanism that automatically indicates to the driver when the tire pressure is too low. One such system is disclosed in U.S. Pat. No. 4,067,376 to Barabino. This patent discloses a high pressure air reservoir provided in the vehicle wheel, and a valve that automatically opens a passageway between the high pressure reservoir and the tire in response to the tire pressure falling below a selected threshold level. In this manner, the tire pressure is automatically prevented from dropping below this level.
Although Barabino's system accomplishes its intended purpose, the valve includes a complicated and expensive porting arrangement which limits its practical commercial application.